Rename several file based on the substring each of them contains.

mass_rename.sh

#!/bin/bash

# Takes all files within current directory and replaces one substring with
# another. This functionality is missing from standard linux shell (maybe
# it is possible to achieve with some complex awk command with regex, but
# I'd prefer to have a plain command for this).
#
#
# e.g. files:
#
# left-hand.txt
# left-hand_01.txt
# left-hand_02.txt
#
# bash mass_rename.sh left-hand right-hand
#
# right-hand.txt
# right-hand_01.txt
# right-hand_02.txt
#
# Add aliast in your bashrc/zshrc file with:
# alias mass_rename='bash X'
# where X is the path this file is stored
#
#TODO: automatize downloading and aliasing the file.

string_orig=$1
string_mod=$2

fileslist=$(ls -1)

for i in $fileslist; do
    if [[ $i == *$string_orig* ]]; then
        new_filename=$(echo $i | sed "s/$string_orig/$string_mod/")
        echo "mv $i $new_filename"
        mv $i $new_filename
    fi
done